1. Technical Field
The present invention relates to a vacuum pump.
2. Background Art
It is required for a rolling bearing rotating at high speed that lubrication of a rolling surface is maintained by continuous supply of a slight amount of lubricant and that adhesion of excessive lubricant to the rolling surface is prevented. When more lubricant than necessary for lubrication adheres to the rolling surface, agitation resistance of the lubricant is caused, leading to heat generation.
A structure described in Patent Literature 1 (Japanese Patent No. 5303137) has been proposed as a bearing device in a vacuum pump. In the bearing device described in Patent Literature 1, lubricant is, through a wick, supplied from a lubricant storage to an inclined outer peripheral surface of a spray nut having a conical surface. The lubricant supplied to the inclined outer peripheral surface of the spray nut moves upward on the inclined surface in association with rotation of the spray nut, and then, is supplied to a rolling bearing held by a bearing holder. Of the lubricant supplied to the rolling bearing, excessive lubricant is guided to a clearance formed between the bearing holder and an outer ring of the rolling bearing, and then, returns to the lubricant storage. The outer ring of the rolling bearing is held by an axial floating ring and a radial floating ring.
In the above-described lubricant supply type bearing device, the amount of lubricant supplied to the bearing is preferably a minimum amount to prevent unnecessary heat generation due to lubricant agitation in the bearing. The bearing device described in Patent Literature 1 is configured on the assumption that the amount of lubricant supplied to the rolling bearing becomes excessive. For this reason, when the amount of lubricant supplied to the rolling bearing is the minimum amount, the effect of releasing, to the outside, friction heat caused between the rolling body and the rolling surface in the bearing by heat transfer of the bearing is lowered, and therefore, there is a probability that a sufficient heat dissipation effect cannot be obtained.